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August 2012

The lights weren’t working on a 400 ft. radio tower. The controller’s enclosure was damaged and water had gotten in.

The board had a fair amount of corrosion, and also some scorch marks.

It looks like there may have been some transients from lightning, as the leads to one of the MOVs has melted.

I toned out the connections, and it matches the typical NE555 oscillation circuit. The damage was mostly limited to the MOVs (150L20), and the TVS protection diode (1N6281C). But, before the TVS blew, it took out a couple of traces on the board. So,I just bodged in a couple of wires to repair the trace, and it’s all running again.